1. Field of the Invention
The invention relates to a vertical internal push broaching machine comprising a machine column having an upper rail and a back wall; carriage guideways mounted on the back wall and disposed in a common vertical plane; a workpiece lifting table displaceably guided on the carriage guide-ways in front of the back wall; a feeder carriage guided for vertical displacement and disposed underneath the lifting table; a lifting table drive connecting the machine column and the lifting table; at least one upper broach holder mounted on the rail; at least one workpiece seat disposed on the lifting table for the accommodation of a workpiece which is to be broached; and at least one lower workpiece holder mounted on the feeder carriage, a workpiece seat and an upper broach holder and a lower broach holder at a time being disposed coaxially of the central longitudinal axis of a broach.
2. Background Art
A broaching machine of the generic type known from U.S. Pat. No. 5,833,411 comprises two elevating spindles which connect the rail and the lifting table and are disposed by their central longitudinal axes in a common plane, the axis of the at least one broach also being disposed in this plane, namely between the two elevating spindles. As a result of this design, the machine column itself is free from forces because the entire broaching forces remain within the system consisting of the lifting table, rail, elevating spindles and broach.
It is an object of the invention to embody the broaching machine of the generic type such that it has a constructionally less complicated design.
According to the invention, this object is attained by the lifting table drive being formed by a single elevating drive which is disposed behind the plane spanned by the carriage guideways. The measures according to the invention help avoid problems that may reside in the existence of two elevating drives. These problems consist in the synchronization of two driving motors for two elevating spindles, and the difference in heating and thus in thermal expansion of the elevating spindles, or the synchronization of two hydraulically actuated piston-cylinder drives. Further, problems of guidance of the lifting table, which may occur in the case of a guidance, free from play, of the lifting table and in the case of actuation by two elevating drives, are avoided by overdetermination of the guidance. Furthermore, a design is obtained which is narrower than in the known embodiment. Avoiding the mentioned drawbacks also results in a reduction of cost.
An advantageous embodiment which is independently inventive resides in that the twist motor comprises a geared motor which is allocated to the feeder carriage and coupled with the lower broach holder.
Further features, advantages and details of the invention will become apparent from the ensuing description of exemplary embodiments, taken in conjunction with the drawing.